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  • 1
    Electronic Resource
    Electronic Resource
    High resolution x-ray spectroscopy using GaAs arrays (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5376-5381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have produced a number of small format gallium arsenide (GaAs) arrays to address the material, electronic, and technological problems that need to be solved in order to develop mega pixel, Fano-limited spectroscopic x-ray imagers. Results will be presented of a series of x-ray measurements carried out on a prototype 5×5 array, fabricated from 40 μm thick epitaxial GaAs. The device has pixel sizes of 200×200 μm2 and pitch 250 μm. As a preliminary investigation of performance, two pixels have been instrumented. Measurements from 5.9 to 98 keV were carried out both in our laboratory and at the Hamburger Synchrotronstrahlungslabor research facility in Hamburg, Germany. Both pixels were found to be remarkably uniform, both in their spectral and spatial response to x-rays. The average nonlinearity in the spectral response is 〈1% across the energy range 5.9–98 keV. Using a 12 keV, 20×20 μm2 pencil beam, the spatial uniformity was found to be better than 98% over the entire pixel surfaces, consistent with the statistical precision of the measurement. The energy resolution at −40 °C is 400 eV full width at half maximum (FWHM) at 5.9 keV rising to 700 eV FWHM at 98 keV. No difference in energy resolution was found between full area and pencil beam illumination. An analysis of the resolution function has shown that the detector is dominated by electronic noise at low energies and Fano noise at energies above 30 keV. By best-fitting the expected resolution function to the entire data set, we derive a Fano factor of 0.140±0.05, together with a charge transport factor as low as 1.4×10−3. Further improvement in the resolution function has been achieved by replacing the conventional resistive feedback preamplifiers with a new resistorless design, which provides a lower component of electronic noise. In this case, a resolution of 266 eV FWHM at 5.9 keV has been achieved at room temperature (23 °C) and 219 eV FWHM with only modest cooling (−31 °C). The expected Fano noise at this energy is ∼140 eV. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1406546
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  • 2
    Electronic Resource
    Electronic Resource
    The soft x-ray transmission properties of thin polyimide windows and their application to future detectors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2570-2573 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The x-ray transmission properties of a very thin polyimide window in the range 7–310 A(ring) have been investigated. The window is nominally 0.24 μm thick and is supported by a hexagonal polyimide grid. Transmission of over 60% and 80% at the oxygen Kα and carbon Kα lines, respectively, have been achieved. The use of such windows as the entrance window of a gas scintillation counter (GSPC) operating as a broadband spectrometer at XUV wavelengths is discussed. Overall detector efficiencies of greater than 10% for wavelengths less than 150 A(ring) are possible to achieve. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145659
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  • 3
    Electronic Resource
    Electronic Resource
    Synchrotron characterization of deep depletion epitaxial GaAs detectors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4341-4347 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a series of synchrotron characterizations of two epitaxial GaAs detectors of active areas 2.22 mm2 and thicknesses 40 and 400 μm. In spite of an order of magnitude difference in depletion depths, the detectors were found to have comparable performances at ∼−40 °C, with energy resolutions of ∼1 keV full width at half maximum (FWHM) at 7 keV rising to ∼2 keV FWHM at 200 keV and noise floors in the range of 1–1.5 keV. At the lower energies, the energy resolution was dominated by leakage current and electromagnetic pickup. At the highest energies, however, the measured resolutions appear to approach the expected Fano limit; e.g., ∼950 eV at 200 keV. Both detectors were remarkably linear, with average rms nonlinearities of 0.2% over the energy range of 10–60 keV. By raster scanning the active areas with 20×20 μm2 monoenergetic photon beams, it was found that the nonuniformity in the spatial response of both detectors was less than 1% and independent of energy. The material used to fabricate the detector is extremely pure. For example, low temperature photoluminescence measurements indicate that the density of the As antisite defect (EL2) is of the order of 1012 cm−3, which is ∼2–3 orders of magnitude lower than that generally reported. This indirect measurement of material purity is confirmed by Monte Carlo simulations of the detector x-ray response, which show that in order to reproduce the observed energy-loss spectra, electron and hole trapping cross-section/density products must be (very-much-less-than)1 cm−1. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371367
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray response of epitaxial GaAs (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7522-7527 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We summarize the results of a number of x-ray experiments on an epitaxial GaAs device carried out in both our laboratory and the Physikalisch-Technishe Bundesanstalt radiometry Laboratory at the Berliner Elektronenspeicherring-Gesellschaft fur Synchrotronstrahlung Synchrotron Radiation Source. The detector has a diameter of 1.5 mm and is fully depleted to a depth of 40 μm. It has been characterized as a function of energy, bias, and temperature. At −35 °C we determine the charge collection efficiency to be 97% and find that energy resolutions ranging from 730 to 930 eV full width at half maximum (FWHM) can be readily achieved using conventional pre-amplifiers over the energy range 6–60 keV. By considering the various contributions to the FWHM, we show that leakage current and charge trapping noise dominate the resolution function. From detector modeling we determine the effective electron and hole density/cross section products to be 7 and 3 cm−1, respectively. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370549
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  • 5
    Electronic Resource
    Electronic Resource
    Light yield as a function of gas pressure and electric field in gas scintillation proportional counters
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 294 (1990), S. 595-601 
    Details
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0168-9002(90)90303-N
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  • 6
    Electronic Resource
    Electronic Resource
    On the X-ray transmission properties of multilayer windows
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 345 (1994), S. 549-560 
    Details
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0168-9002(94)90515-0
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  • 7
    Electronic Resource
    Electronic Resource
    Imaging multielement analysis with synchrotron radiation excited X-ray fluorescence radiation
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 266 (1988), S. 308-312 
    Details
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0168-9002(88)90402-0
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  • 8
    Electronic Resource
    Electronic Resource
    Coded imaging x-ray microprobe (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 65-70 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An experimental comparison is presented between line scanning (coded imaging) and conventional point scanning (direct imaging), based on experience gained with an x-ray microprobe operated at the Hamburger Synchrotronstrahlungs-Laboratorium (HASYLAB) at the Deutsches Elektronen-Synchrotron (DESY). The microprobe uses synchrotron radiation to excite x-ray fluorescence radiation in the sample, which is detected by a solid-state detector and analysed for the element composition of the sample. The spatial distribution of elements, even if present only in traces, may be measured on a microscopic scale. Both methods were evaluated with regard to their imaging properties and compared with each other. The line-scanning technique is shown to have a better signal-to-noise ratio, thus achieving a superior image quality. Some sample applications are described for illustration.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220203
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  • 9
    Electronic Resource
    Electronic Resource
    Experiments on imaging X-ray analytical methodsPaper presented at ECASIA 87, Stuttgart, FRG, 19-23 october 1987. (1989)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 163-169 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: X-ray induced analysis of matter offers solutions to a great variety of analyst's questions in various disciplines. Based on the physical nature of primary interaction (photoelectric absorption, elastic/inelastic scattering) and on the secondary specimen response (modulated primary radiation, fluorescent radiation, photoelectrons, Auger electrons), a powerful family of different analytical techniques has evolved. This paper emphasizes the methods of x-ray photoeletron spectrometry (XPS) and x-ray fluorescence analysis (XRF), covering depth information ranging from ca. 1 nm (XPS) to 〉 10 μm (XRF). Scanning schemes to extract spatial resolution of the specific analytical signal are presented. These methods operate in (hardware-based) line-selection modes during data acquisition and are essentially based on computer-(software-)aided data decoding to achieve point information (element map). Operating principles, alternative concepts, experimental set ups, results and some future trends are summarized.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740140402
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  • 10
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    The soft x‐ray transmission properties of thin polyimide windows and their application to future detectors (1995)
    American Institute of Physics
    Details
    Publication Date: 1995-03-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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